How the brain detects the emotions of others

People who are good at interpreting facial expressions have “mirror neuron” systems that are more active, say researchers. The finding adds weight to the idea that these cells are crucial to helping us figure out how others are feeling.

Mirror neurons are brain cells that fire both when you do something and when you watch someone else do the same thing.

Because they allow us to mimic what others are doing, it is thought that these neurons may be responsible for why we can feel empathy, or understand others’ intentions and states of mind. People with autism, for instance, show reduced mirror neuron activity during social cognition tasks.

Now Peter Enticott at Monash University in Melbourne, Australia, and his colleagues have found evidence supporting this theory. They asked 20 healthy adults to look at pairs of images. In one task, they had to decide if paired images of faces were the same person. In another, they had to decide if both faces were showing the same emotion.

In a separate task, volunteers watched video clips of thumb movement, a hand grasping a pen and a hand while writing, while the activity in the primary motor cortex of the brain, which contains mirror neurons, was recorded.

Emotional link

Now the team had a measure of the “motor potential” in the thumb muscles – for example, how much the thumb was primed to move just by watching another thumb moving. This measure is a proxy for mirror neuron activity, say the researchers.

Enticott’s team found that the volunteers who were better at judging people’s emotions had higher mirror neuron activity in the thumb task. There was no correlation, however, between the ability to recognise faces and mirror neuron activity. This suggests that mirror neurons are involved in understanding emotions as well as in the mimicry of actions.

“[The study] connects the two different functions – the motor aspect with the emotional processing aspect,” says Lindsay Oberman, at Beth Israel Deaconess Hospital in Boston, Massachusetts, US. “They show that mirror neurons for motor activity are related to mirror neurons for emotions,” she adds.